Process for producing organic thin film

ABSTRACT

A wrinkle-free organic film having a high light transmittance and a uniform film thickness is obtained by forming an organic thin film on the surface of a substrate having a contact angle of the surface to water of 90° or higher, followed by peeling the film therefrom.

BACKGROUND OF THE INVENTION

[0001]1) Field of the Invention

[0002] The present invention relates to an organic thin film obtained byforming an organic thin film on a substrate followed by peeling the filmtherefrom, and a process for producing an organic thin film, whichcomprises forming an organic thin film on a substrate, followed bypeeling the film therefrom, where the peeling can be made easily.

[0003]2) Description of the Related Art

[0004] One example of organic thin film obtained by forming an organicthin film on a substrate, followed by peeling the film therefrom is apellicle, which can be used by fixing it to a photo mask or a reticleused in the photolithographic process in the production of semiconductorintegrated circuits, and the photo mask or reticle will be hereinafterreferred to merely as “mask”.

[0005] The pellicle is a dust cover for photomasks or reticles for usein production of large-scale integration circuits and substrates forliquid crystals.

[0006] The pellicle is provided above the mask at a specific distancefrom the mask. Thus, even if fine foreign matters, etc. are attached tothe pellicle in the photolithographic process, none of their images isprojected on a photoresist-coated semiconductor wafer. That is, byprotecting a mask by a pellicle, short circuits, disconnection, etc. ofsemiconductor integrated circuits can be protected, thereby improvingproduction yields of photolithographic process, and furthermore reducingnumber of mask cleaning operations, which leads to prolonged mask life.It is the pellicle that can attain such effects.

[0007] Light source for irradiation in the photolithographic processincludes an ultrahigh pressure mercury lamp, and its g line (λ=436 nm),h line (λ=405 nm) and i line (λ=365 nm) are used as emission lines forthe irradiation.

[0008] With recent technological progress in the semiconductor industry,integrated circuits of higher density and higher degree of integrationare now available and projection patterns with smaller line width andinterline distance on a wafer are also now available. Consequently,light sources for irradiation with shorter wavelength are utilized now.For example, far ultraviolet rays (Deep UV) by an excimer laser ofkrypton fluoride (KrF), argon fluoride (ArF), etc. can be used. To meetthe light sources of shorter wavelength, light-stable pelliclestransparent to such higher energy radiation beams are now keenlydesired.

[0009] To meet such requirements, pellicles composed of fluorine-basedmaterials or silicon-based materials have been proposed. The materialsinclude, for example, fluorine-based materials such astetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymers(JP-B63-27707), fluorine-based polymers having a perfluoro-alkyl etherring structure, i.e. CYTOP (trademark of a product commerciallyavailable from Asahi Glass Co., Ltd., Japan), Teflon AF (trademark of aproduct commercially available from E.I. du Pont de Nemours & Co., Inc.,USA), etc., and polymeric organosilicone compounds such aspolytrimethylvinylsilane, etc. (JP-A-2-230245), etc.

[0010] A reflection-preventing single, double or multiple layer can beprovided on one side or both sides of a pellicle.

[0011] Materials proposed for a reflection-preventing layer(s) as anoutermost layer(s) include, for example, tetrafluoroethylene-vinylidenefluoridehexafluoro-propylene polymer (JP-A-61-209449),polyfluoroacrylate (JP-A-1-100549), fluoropolymer having a ringstructure on the principal chain, i.e. Teflon AF (trademark of a productcommercially available from E.I. du Pont de Nemours & Co., Inc., USA,JP-A-3-39963), CYTOP (trademark of a product commercially available fromAsahi Glass Co., Ltd., Japan), etc.

[0012] Most of the materials for the outermost reflection-preventinglayer are fluorine-containing polymers or inorganic fluorine materialssuch as calcium fluoride, magnesium fluoride, etc. Most of materials fora transparent thin film layer (central layer) are cellulose derivativessuch as nitrocellulose, cellulose acetate propionate, carbonated acetylcellulose, etc.

[0013] Such a pellicle has been so far produced by forming a film fromsuch pellicle materials as mentioned above on a smooth substrate ofglass, quartz, Si wafer or the like, followed by peeling it therefrom. Apellicle composed of fluorine-based materials or silicon-basedmaterials, when formed on the substrate, has a high adhesiveness to thesubstrate, so that the film is hard to peel from the substrate, therebyleading the film to breaking or wrinkling.

[0014] When a pellicle film is to be formed on a substrate by formingthe outermost reflection-preventing layer and so on successively in thisorder, the outermost reflection-preventing layer is hard to peel fromthe substrate, because it is composed of fluorine-based materials andconsequently has a high adhesiveness to the substrate.

[0015] So far proposed methods for peeling the film from the substrateinclude, for example, a method for peeling by dipping into water(JP-A-58-219023; JP-A-60-35733; JP-A-2-64, etc.), a method for peelingby dipping in a chemical solution and then in water (JP-A-56-83941), amethod for peeling from a substrate in a wet state (JP-A-62-39859), amethod for peeling in an atmosphere at a relative humidity of 60% orhigher (JP-A-6-67410), a method for peeling upon cooling to 5° C. orlower (JP-A-1-166045), etc.

[0016] However, peeling by the above-mentioned methods have suchproblems as deterioration of light transmissivity, uneven filmthickness, etc. Particularly, dipping into water or chemical solutionhas such problems as contamination of pellicle films and deteriorationof light transmittance. Peeling in a wet state or in an atmosphere at arelative humidity of 60% or higher has such problems as unevenness offilm thickness (color unevenness and difficult process control besidesthe problem of deteriorated light transmittance due to the fouling ofpellicle film. Furthermore, peeling upon cooling to 5° C. or lower hassuch problems as a failure to obtain desired effects, depending onpellicle materials, process complication, etc.

[0017] Substrate that has been once peeled off the pellicle film hassuch a problem as contamination of substrate surface, and thus thefilm-peeled substrate must be cleaned or repolished before its reuse.

SUMMARY OF THE INVENTION

[0018] An object of the present invention is to provide a wrinkle-freeorganic thin film having a high light transmittance and a uniform filmthickness and also to provide a process for producing an organic thinfilm readily peelable from the substrate, the substrate being repeatedlyreusable as a recycle substrate, as distinguished over theabove-mentioned prior art.

[0019] As a result of extensive studies to solve the above-mentionedprior art problems, the present inventors have found that a wrinkle-freeorganic thin film having a high light transmittance and a uniform filmthickness can be obtained by forming an organic thin film on the surfaceof a substrate having a contact angle of the surface to water of 90° orhigher, or particularly an organic thin film comprising a fluorine-basedmaterial or a silicon-based material on a substrate having a specificsilicon compound on the surface, thereby making the formed organic thinfilm readily peelable from the substrate, and the substrate that hasbeen peeled off the film repeatedly reusable as a recycle substrate, andhave established the present invention.

[0020] A first aspect of the present invention is to provide an organicthin film obtained by forming an organic thin film on the surface of asubstrate having a contact angle of the surface to water of 90° orhigher, followed by peeling the film therefrom.

[0021] A second aspect of the present invention is to provide an organicthin film obtained by forming an organic thin film comprising afluorine-based material or a silicon-based material on the surface of asubstrate having a layer comprising a silicon compound having aperfluoroalkyl group formed on the surface, followed by peeling the filmtherefrom.

[0022] A third aspect of the invention is to provide an organic thinfilm according to the first or second aspect of the present invention,wherein the organic thin film is in a single layer.

[0023] A fourth aspect of the present invention is to provide an organicthin film according to any one of the first to third aspects of thepresent invention, wherein the organic thin film is a pellicle.

[0024] A fifth aspect of the present invention is to provide an organicthin film according to the first, second or fourth aspect of the presentinvention, wherein the organic thin film is a pellicle comprising areflection-preventing layer composed of a fluorine-based material and atransparent thin film layer.

[0025] A sixth aspect of the present invention is to provide an organicthin film according to any one of the second to fourth aspects of thepresent invention, wherein the layer comprising a silicon compoundhaving a perfluoroalkyl group is formed by vapor deposition.

[0026] A seventh aspect of the present invention is to provide anorganic thin film according to any one of the second to fourth aspectsof the present invention, wherein the silicon compound having aperfluoroalkyl group is a compound represented by the following formula(1):

CF₃(CF₂)_(n)CH₂CH₂Si(OMe)₃  (1)

[0027] where n is an integer of 5 to 7 and Me is a methyl group.

[0028] An eighth aspect of the present invention is to provide a processfor producing an organic thin film, which comprises forming an organicthin film on the surface of a substrate having a contact angle of thesurface to water of 90° or higher, followed by peeling the filmtherefrom.

[0029] A ninth aspect of the present invention is to provide a processfor producing an organic thin film, which comprises forming an organicthin film comprising a fluorine-based material or a silicon-basedmaterial on the surface of a substrate having a layer comprising asilicon compound having a perfluoroalkyl group formed on the surface,followed by peeling the film therefrom.

[0030] A tenth aspect of the present invention is to provide a processfor producing an organic thin film according to the eighth or ninthaspect of the present invention, wherein the organic thin film is in asingle layer.

[0031] An eleventh aspect of the present invention is to provide aprocess for producing an organic thin film according to any one of theeighth to tenth aspects of the present invention, wherein the organicthin film is a pellicle.

[0032] A twelfth aspect of the present invention is to provide a processfor producing an organic thin film according to the eighth, ninth oreleventh aspect of the present invention, wherein the organic thin filmis a pellicle comprising a reflection-preventing layer composed of afluorine-based material and a transparent thin film layer.

[0033] A thirteenth aspect of the present invention is to provide aprocess for producing an organic thin film according to any one of theninth to eleventh aspects of the present invention, wherein the layercomprising a silicon compound having a perfluoroalkyl group is formed byvapor deposition.

[0034] A fourteenth aspect of the present invention is to provide aprocess for producing an organic thin film according to any one of theninth to eleventh aspects of the present invention, wherein the siliconcompound having a perfluoroalkyl group is a compound represented by thefollowing formula (1):

CF₃(CF₂)_(n)CH₂CH₂Si(OMe)₃  (1)

[0035] where n is an integer of 5 to 7 and Me is a methyl group.

[0036] The present invention provides a wrinkle-free organic thin filmhaving a high light transmittance and a uniform film thickness and aprocess for producing an organic thin film readily peelable from asubstrate, the substrate being repeatedly reusable as a recyclesubstrate. Particularly by forming a layer comprising a silicon compoundhaving a perfluoroalkyl group on the substrate by vapor deposition anorganic thin film having a good surface smoothness, and a very highlight transmittance and particularly readily peelable from the substratecan be obtained.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] Substrate for use in the formation of the present organic thinfilm includes those composed of glass such as soda lime, etc., quartz,Si wafer, etc. The substrate must have a sufficiently smooth surface.

[0038] The substrate for use in the present invention is a substrate sotreated as to give a contact angle of the substrate surface to water of90° or higher or a substrate originally having a contact angle to waterof 90° or higher.

[0039] The contact angle of the substrate surface to water means anangle formed between the substrate surface and a tangential line drawnto the top free side of a water droplet on the substrate surface at thecontact point of the substrate surface and the down contact side of thewater droplet on the substrate surface, the angle covering the entireperiphery of water droplet. The water droplet is of pure water.

[0040] Any treating procedure can be used to make the contact angle ofthe substrate surface to water 90° or higher, including, for example,formation of a layer comprising a silicon compound having aperfluoroalkyl group on the surface of a substrate. Such formation of asilicon compound having a perfluoroalkyl group on the substrate can bemade by any procedure, but preferably by spin coating or vapordeposition, more preferably by vapor deposition.

[0041] Vapor deposition means deposition of vapors of a silicon compoundhaving a perfluoroalkyl group onto a substrate.

[0042] Vapor deposition of a silicon compound having a perfluoroalkylgroup onto a substrate can be carried out under an atmospheric,subatmospheric or superatmospheric pressure. A silicon compound having aperfluoroalkyl group and a substrate are placed into a container, wherethe substrate is formed with vapors of the silicon compound having aperfluoroalkyl group preferably under an atmospheric or subatmosphericpressure at a forming temperature of preferably 5 to 200° C., morepreferably 20° to 130° C. The container is preferably tightly sealed,but may have a ventilation port to the outside. Forming time ispreferably one minute to one week, more preferably one hour to 3 days.

[0043] Substrate having a layer comprising a silicon compound having aperfluoroalkyl group formed on the surface is used as a substrate forforming an organic thin film thereon.

[0044] Silicon compound having a perfluoroalkyl group includes, thoserepresented by the following formulae (2), (3), (4) and (5):

CF₃(CF₂)₇CH₂CH₂Si(OMe)₃  (2)

CF₃(CF₂)₅CH₂CH₂Si(Ome)₃  (3)

CF₃(CF₂)₇CH₂CH₂SiMe(OMe)₂  (4)

CF₃(CF₂)₅CH₂CH₂SiMe (OMe)₂  (5)

[0045] where Me is a methyl group; silazanes having a perfluoroalkylgroup; and their oligomers, etc.

[0046] Among these compounds, the compound represented by the foregoingformula (2) (i.e.10,10,10,9,9,8,8,7,7,6,6,5,5,4,4,3,3-heptadecafluoro-decyltrimethoxysilane)is particularly preferable.

[0047] An organic thin film is formed on the substrate having a layer ofsilicon compound having a perfluoro-alkyl group formed thereon by vapordeposition.

[0048] Thickness of the organic thin film so formed is 50 μm or less,preferably 10 μm or less.

[0049] The present organic thin film can be formed by any procedure, butspin coating is preferable because of distinguished precision of filmthickness and surface characteristics. Spin coating depends on manyfactors such as solution viscosity; solvent evaporation rate, spincoater surrounding temperature and humidity, spin revolutions perminute, spin time, etc., and thus the factors must be properly selected.

[0050] Materials for the organic thin film are the above-mentionedfluorine-based materials and silicon-based materials such astetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer,CYTOP, Tefron AF, polytrimethylvinylsilane, polytriethylvinylsilane,polyethyldimethylvinylsilane, etc. These materials can be used alone orin mixture of at least two thereof.

[0051] When the organic thin film is in the form of pellicle, thesematerials can be irradiated with light, for example, radiations such asγ-rays, electron beams, α-rays, etc., or far ultraviolet rays or thelike to improve the solution filtrability, electric controllability,adhesiveness to pellicle support frame, etc.

[0052] Solvent for the fluorine-based materials includes, for example,perfluoroalkane, perfluorobenzene, perfluoro (2-butyltetrahydrofuran),trichlorotrifluoroethane, perfluorotripropylamine,perfluorotributylamine, etc. and mixtures thereof.

[0053] Solvent for the silicon-based materials includes, for example,benzene, toluene, xylene, etc. Boiling point of these solvents ispreferably 70° C. or higher, more preferably 100° C. or higher.

[0054] Solution of the materials for the organic thin film must besubjected to spin coating after filtration to remove foreign matters,etc. The thickness of the resulting organic thin film can be properlyselected by changing the solution viscosity and revolutions per minuteof the substrate. The solvent contained in the organic thin film formedon the substrate can be evaporated off by a hot plate, an oven etc.

[0055] The organic thin film formed on the substrate is then bonded to adouble faced tape-pasted support frame of metal, plastic, etc. at roomtemperature in air. Then, the organic thin film can be obtained bypeeling the support frame from the substrate. Since the substrate has acontact angle of the surface to water of 90° or higher obtained by vapordeposition of the silicon compound having a perfluoroalkyl group on thesurface of the substrate, the wrinkle-free organic thin film having ahigh light transmittance and a uniform thickness can be peeled from thesubstrate.

[0056] Furthermore, the substrate that has been peeled off the organicthin film can be repeatedly reused as a recycle substrate directlywithout cleaning for further formation of organic thin films, followedby peeling.

[0057] When the organic thin film is in the form of a pellicle, thepellicle can be bonded to the support frame, by an ultraviolet curingtype adhesive, a thermosetting type adhesive or the like or by meltbonding or by a thick polymer solution as an adhesive.

[0058] In case of a pellicle having a single reflection-preventing layeron both sides, a reflection-preventing layer is at first formed on thesubstrate and, after thorough solvent evaporation from thereflection-preventing layer by drying, a transparent thin film layer(central layer) is then formed on the reflection-preventing layer. Afterthorough solvent evaporation from the transparent thin film layer bydrying, another reflection-preventing layer is formed thereon. Thetriple layer film thus formed on the substrate is bonded to a doublefaced tape-pasted support frame of metal, plastic, etc. By peeling thesupport frame from the substrate, a pellicle triple layer film can beeasily obtained thereby, because the silicon compound having aperfluoroalkyl group has been vapor deposited on the substrate surfacein advance.

[0059] A pellicle having a double reflection-preventing layer on bothsides can be likewise obtained by successively forming a low refractiveindex, reflection-preventing layer, a high refractive index,reflection-preventing layer, a transparent thin film layer (centrallayer), a high refractive index, reflection-preventing layer and a lowrefractive index, reflection-preventing layer on a substrate, bonding asupport frame thereto, followed by peeling from the substrate. Thefive-layered film as bonded to the support frame can be easily obtained.

[0060] Materials for the transparent thin film layer (central layer)include, for example, cellulose derivatives such as nitrocellulose,cellulose acetate, cellulose acetate butyrate, cellulose acetatepropionate, ethyl cellulose, carbonated acetyl cellulose, etc. Thecellulose derivatives can be used alone, but nitro-cellulose has adistinguished film strength and a form retainability at a high humiditybut has a poor light stability, as compared with other cellulosederivatives. Cellulose acetate, cellulose acetate propionate andcellulose acetate butyrate have a distinguished light stability, buthave a poor film strength and a poor form retainability at a highhumidity. Thus, it is preferable to use a mixture of nitrocellulose andat least one of other cellulose derivatives.

[0061] A mixing proportion of nitrocellulose to at least one of othernitrocellulose depends on the desired film strength, form retainabilityat a high humidity and light stability, but the nitrocellulose contentof the mixture is preferably 10 to 50% by weight, more preferably 20 to40% by weight. It is preferable to use cellulose derivatives having ahigher molecular weight, because of a better form retainability of thethin film. That is, the molecular weight is 30,000 or more, preferably50,000 or more in terms of number average molecular weight. Among thecellulose derivatives, nitrocellulose is commercially available fromAsahi Chemical Industry Co., Ltd., Japan, and cellulose acetate,cellulose acetate butyrate and cellulose acetate propionate arecommercially available from Eastman-Kodak Co., USA.

[0062] Solvent for the cellulose derivatives includes, for example,2-butanone, methyl isobutyl ketone, cyclohexanone, butyl acetate,isobutyl acetate, ethyl lactate, cellosolve acetate, propyleneglycolmonomethyl ether acetate, etc. and a mixture thereof. Solutions ofcellulose derivatives are subjected to spin coating after filtration toremove foreign matters therefrom. Thickness of the transparent thin film(central layer) can be properly selected by changing the solutionviscosity and revolutions per minute of the substrate. The solventcontained in the thin film formed on the substrate can be evaporated offby a hot plate, an oven, etc.

[0063] The reflection-preventing layer is in a single or double ormultiple layer structure. In case of a single layer reflectionprevention [the number of layers in a pellicle will be 3 (triple layer)when the reflection-preventing layer is formed on both sides of thetransparent thin film layer], the reflection-preventing effect will be amaximum when the relation between the refractive index n₁ of thereflection-preventing layer and the refractive index n_(c) of thetransparent thin film (central layer) is n₁=(n_(c))^(½), and a largerreflection-preventing effect can be obtained by selectingreflection-preventing materials having a refractive index n₁ nearer to(n_(c))^(½). Let the reflection-to-prevent wavelength be λ, thickness dof the reflection-preventing layer must be selected to satisfy arelation of n₁·d=λ/4.

[0064] In case of a double layer reflection prevention (the number oflayers in a pellicle will be 5 when the double reflection-preventinglayer is formed on both sides of the transparent thin film layer as inthe same manner as above), the layer in contact with the transparentthin film layer will be a high refractive index, reflection-preventinglayer and the outermost layer will be a low refractive index,reflection-preventing layer. Let the refractive indices and thicknessesof the outermost reflection-preventing layer and thereflection-preventing layer in contact with the transparent thin filmlayer be n₁ and d₁, and n₂ and d₂, respectively, thereflection-preventing effect will be a maximum, when n₂/n₁=(n_(c))^(½),and a larger reflection-preventing effect can be obtained by selectingreflection-preventing layer materials having n₂/n₁ nearer to(n_(c))^(½). Let the reflection-to-prevent wavelength be λ, thicknessesd₁ and d₂ of the reflection-preventing layers must be selected tosatisfy a relation of n₁·d₁=n₂·d₂=λ/4. For the central layer, cellulosederivatives, polyvinylbutyral, polyvinylpropional, etc. can be used,where their refractive indice n_(c) are about 1.5, and thus (n_(c))^(½)will be about 1.22. That is, in case of the double layer reflectionprevention, a larger reflection-preventing effect can be obtainedpreferably, when materials for the double reflection-preventing layerare selected to have a ratio of their refractive indice n₂/n₁ nearer to1.22.

[0065] Materials for the low refractive index, reflection-preventinglayer for use as the outermost layer include, for example,fluorine-based materials such as tetrafluoroethylene-vinylidenefluoride-hexafluoropropylene polymer, polyfluoroacrylate, Teflon AF(trademark of fluorine-based polymer having a cyclic structure on theprincipal chain, commercially available from E.I. du Pont de Nemours &Co., Inc., USA), CYTOP (trademark of a product commercially availablefrom Asahi Glass Co., Ltd., Japan), etc. Preferable polyfluoroacrylateis FC-722 (trademark of a product commercially available from Sumitomo3M Co., Ltd., Japan). In case of Teflon AF, filtrability, electriccontrollability and adhesiveness between the pellicle film and thesupport frame can be improved by irradiation of light such asradiations, e.g. γ-rays, electron beams, α-rays, etc., or farultraviolet rays or the like.

[0066] The fluorine-based materials for the reflection-preventing layercan be used alone or in mixture of other polymers. The fluorine-basedpolymer is dissolved into a fluorine-based solvent such asperfluorobenzene, perfluoro (2-butyltetrahydrofuran),trichlorotrifluoroethane, perfluorotributylamine, etc., but to obtain asmooth film surface free from color unevenness a high boiling pointsolvent is preferable. The boiling point is preferably 130° C. orhigher, more preferably 160° C. or higher.

[0067] The fluorine-based polymer solution is subjected to spin coatingafter filtration to remove foreign matters therefrom in advance.Thickness of low refractive index, reflection-preventing layer for useas the outermost layer can be properly selected by changing the solutionviscosity and revolutions per minute of the substrate. The solventcontained in the thin film formed on the substrate can be evaporated offby air drying or by a hot plate, an oven, etc.

[0068] In case of the double layer reflection-preventing pellicle,materials for the high refractive index, reflection-preventing layer incontact with the transparent thin film layer include, for example,polyvinylnaphthalene, polystyrene, polyether sulfone, etc. The pelliclewith the reflection-preventing layers can be bonded to a support frameby an adhesive such as an ultraviolet-curing type adhesive or athermosetting type adhesive. It is preferable to use anultraviolet-curing type adhesive because of process simplicity and lessdamage to the pellicle film.

[0069] The present invention will be described in detail below,referring to Examples and Comparative Examples.

EXAMPLE 1

[0070] An open top, polyethylene container, 5 cm in diameter, containing20 ml of10,10,10,9,9,8,8,7,7,6,6,5,5,4,4,3,3-heptadecafluoro-decyltrimethoxysilaneand a polished silicon wafer were placed into a 30 cm-square metallicvessel, followed by tight sealing. The metallic vessel and its insidewere heated to 105° C., left for standing in that state for 36 hours,and cooled to room temperature, and the treated silicon wafer was takenout of the metallic vessel. The treated silicon wafer had a contactangle of the surface to water of 110°, whereas the untreated polishedwafer had a contact angle of 51°.

[0071] Then, CYTOP, S grade (trademark of a product commerciallyavailable from Asahi Glass Co., Ltd., Japan) was dissolved intoperfluorotributylamine to make a 5.0 wt. % CYTOP solution.

[0072] Then, the treated silicon wafer was set to a spin coater, and theCYTOP solution was filtered through a membrane filter having a pore sizeof 0.2 μm and the filtrate was subjected to spin coating, followed bydrying on a hot plate, whereby an organic thin film having a thicknessof 0.84 μm was formed.

[0073] Then, a double faced tape-pasted metallic support frame wasbonded to the organic thin film formed on the silicon wafer and peeledfrom the silicon wafer at 23° C. and a relative humidity of 50%, wherebythe organic thin film could be easily peeled from the silicon wafer.

[0074] The resulting organic thin film was free from wrinkles and alsofrom any color unevenness or transferred matters from the substrate, andwas thus found satisfactory. The light transmittance at the wavelengthof about 248 nm was as high as 99.9%, and the film thickness was uniformand satisfactory.

[0075] The silicon wafer surface that was peeled off the organic thinfilm, which will be hereinafter referred to as “recycle silicon wafer”,had no traces of peeling and had the same contact angle of the surfaceto water of 110° C. as that before the organic thin film formation.

[0076] A second organic thin film was formed on the recycle siliconwafer by spin coating in the same manner as before, likewise followed bybonding a double faced tape-pasted metallic support frame to the secondorganic thin film formed on the recycle silicon wafer and peeling of thesupport frame from the recycle silicon wafer at 23° C. and a relativehumidity of 50%, whereby the second organic thin film could be easilypeeled therefrom.

[0077] The resulting second organic thin film was free from wrinkles andalso from any color unevenness or transferred matters from the substrateand was thus found satisfactory. The light transmittance at thewavelength of about 248 nm was also as high as 99.9%, and the filmthickness was also uniform and satisfactory.

[0078] The recycle silicon wafer surface that was peeled off the secondorganic thin film also had no traces of peeling and had a contact angleof the surface to water of 110° C.

[0079] Further organic thin films were repeatedly formed on the samerecycle silicon wafer that was peeled off the organic thin film justbefore in the same manner as above, followed by peeling the just formedorganic thin film, and it was found that 30 recyclic uses of the samerecycle silicon wafer could be made.

[0080] The resulting organic thin films were all free from any wrinkles,color unevenness, traces of peeling or transferred matters from thesubstrate and were thus found satisfactory. The light transmittance atthe wavelength of about 248 nm was also as high as or higher than 99.8%and the film thickness was also satisfactory.

[0081] Even after the 30 recyclic uses, the silicon wafer surface wasfree from traces of peeling and also had the same contact angle of thesurface to water of 110° as before the formation of the organic thinfilms.

EXAMPLE 2

[0082] As in Example 1,10,10,10,9,9,8,8,7,7,6,6,5,5,4,4,3,3-heptadecafluoro-decyltrimethoxysilaneand a polished silicon wafer were placed into a metallic vessel,followed by light sealing. The metallic vessel and its inside wereheated to 30° C., left for standing in that state for 24 hours, andcooled to room temperature, and the treated silicon wafer was taken outof the metallic vessel. The treated silicon wafer had a contact angle ofthe surface to water of 103°, whereas the untreated polished siliconwafer had a contact angle of 51°.

[0083] Then, Teflon AF 1600 (trademark of a product commerciallyavailable from E.I. du Pont de Nemours & Co., Inc., USA) was irradiatedwith γ-rays in air at an irradiation dose of 50 kGy (Gy: dose unit),which will be hereinafter referred to as “γAF 1600”. The γAF 1600 wasdissolved into refluorotributylamine to make a 5.0 wt. % γAF 1600solution.

[0084] Then, the treated silicon wafer was set to a spin coater, and theγAf 1600 solution was filtered through a membrane filter having a poresize of 0.2 μm, and the filtrate was subjected to spin coating, followedby drying on a hot plate, whereby an organic thin film having athickness of 0.84 μm was formed.

[0085] As in Example 1, a double faced tape-pasted metallic supportframe was bonded to the organic thin film formed on the silicon waferand removed together with the organic thin film from the silicon waferat 23° C. and a relative humidity of 50%, whereby the organic thin filmcould be easily peeled from the silicon wafer.

[0086] The resulting organic thin film was free from any wrinkles, colorunevenness, traces of peeling, and transferred matters from thesubstrate and was thus found satisfactory. The light transmittance atthe wavelength of about 248 nm was as high as 99.5% and the filmthickness was uniform and satisfactory.

[0087] The silicon wafer surface that was peeled off the organic thinfilm had no traces of peeling and a contact angle of the surface towater of 103°, and the silicon wafer was repeatedly used as recyclesilicon wafer.

[0088] Then, further organic thin films were repeatedly formed on thesame recycle silicon wafer that was peeled off the organic thin filmjust before in the same manner as above, followed by peeling the justformed organic thin film, and it was found that 10 recyclic uses of thesame recycle silicon wafer could be made.

[0089] The resulting organic thin films were all free from any wrinkles,color unevenness, traces of peeling and transferred matters from thesubstrate and were thus found satisfactory. The light transmittance atthe wavelength of 248 nm was as high as 99.5% and the film thickness wasuniform and satisfactory.

[0090] Even after the 10 recyclic uses, the silicon wafer surface wasfree from traces of peeling and also had the same contact angle of thesurface to water of 103° as before the formation of the organic thinfilms.

EXAMPLE 3

[0091] As in Example 2,10,10,10,9,9,8,8,7,7,6,6,5,5,4,4,3,3-heptadecafluoro-decyltrimethoxysilaneand a polished silicon wafer were placed into a metallic vessel,followed by tight sealing. The metallic vessel and its inside wereheated to 30° C., left for standing in that state for 24 hours, andcooled to room temperature, and the treated silicon wafer was taken outof the metallic vessel. The treated silicon wafer had a contact angle ofthe surface to water of 103°, whereas the untreated polished siliconwafer had a contact angle of 51°.

[0092] As in Example 2, an organic thin film was formed on the treatedsilicon wafer, using the γAf 1600 solution. A double faced tape-pastedmetallic support frame was bonded to the organic thin film formed on thesilicon wafer and the organic thin film could be easily peeled from thesilicon wafer at 23° C. and a relative humidity of 50%.

[0093] The resulting organic thin film was free from any wrinkles, colorunevenness, and transferred matters from the substrate and was thusfound satisfactory. The light transmittance at the wavelength of 248 nmwas as high as 99.6% and the film thickness was uniform andsatisfactory.

[0094] The silicon wafer surface that was peeled off the organic thinfilm had no traces of peeling and had a contact angle of the surface towater of 103°, and the silicon wafer was repeatedly used as a recyclesilicon wafer.

[0095] Further organic thin films were repeatedly formed on the samerecycle silicon wafer that was peeled off the organic thin film justbefore in the same manner as above, followed by peeling the just formedorganic thin film, and it was found that 10 recyclic uses of the samerecycle silicon wafer could be made.

[0096] The resulting organic thin films were all free from any wrinkles,color unevenness, traces of peeling and transferred matters from thesubstrate and were thus satisfactory. The light transmittance at thewavelength of 248 nm was a high as 99.6% and the film thickness wasuniform and satisfactory.

[0097] Even after the 10 recyclic uses, the silicon wafer surface wasfree from traces of peeling and also had the same contact angle of thesurface to water of 103° as before the formation of the organic thinfilms.

EXAMPLE 4

[0098]10,10,10,9,9,8,8,7,7,6,6,5,5,4,4,3,3-heptadecafluorodecyltrimethoxysilaneand a polished silicon wafer were placed into a metallic vessel,followed by tight sealing under inside vessel pressure of 660 mm Hg(−100 mm Hg). The metallic vessel and the inside were heated to 30° C.,left for standing in that state for 24 hours, and cooled to roomtemperature, and the treated silicon wafer was taken out of the metallicvessel. The treated silicon wafer had a contact angle of the surface towater of 104°, whereas the untreated polished silicon wafer had acontact angle of 51°.

[0099] As in Example 2, an organic thin film was formed on the treatedsilicon wafer by spin coating, using the γAF 1600 solution. A doublefaced tape-pasted metallic support frame was bonded to the organic thinfilm formed on the silicon wafer and peeled from the silicon wafer at23° C. and a relative humidity of 50%, whereby the organic thin filmcould be easily peeled from the silicon wafer.

[0100] The resulting organic thin film was free from any wrinkles, colorunevenness, traces of peeling and transferred matters from the substrateand was thus found satisfactory. The light transmittance at thewavelength of about 248 nm was as high as 99.6% and the film thicknesswas uniform and satisfactory.

[0101] The silicon wafer surface that was peeled off the organic thinfilm had no traces of peeling and had a contact angle of the surface towater of 104°. The silicon water was repeatedly used as a recyclesilicon wafer.

[0102] Further organic thin films were repeatedly formed on the samerecycle silicon wafer that was peeled off the organic thin film justbefore in the same manner as above, followed by peeling the just formedorganic thin film, and it was found that 10 recyclic uses the samerecycle silicon wafer could be made.

[0103] The resulting organic thin films were all free from any wrinkles,color unevenness, traces of peeling and transferred matters from thesubstrate and were thus found satisfactory. The light transmittance atthe wavelength of 248 nm was as high as or higher than 99.6% and thefilm thickness was uniform and satisfactory.

[0104] Even after the 10 recyclic uses, the silicon wafer surface had notraces of peeling and had the same contact angle of the surface to waterof 104° as before the formation of the organic thin films.

EXAMPLE 5

[0105] A compound represented by the following formation (3):

CF₃(CF₂)₅CH₂CH₂Si(OMe)₃  (3)

[0106] where Me is a methyl group, and a polished silicon wafer wereplaced into a metallic container, followed by tight sealing. Themetallic container and its inside were heated to 105° C., left forstanding in that state for 36 hours, and cooled to room temperature andthe treated silicon wafer was taken out of the metallic container. Thetreated silicon wafer had a contact angle of the surface to water of108°, whereas the untreated polished silicon wafer had a contact angleof 51°.

[0107] As in Example 2, an organic thin film was formed on the treatedsilicon wafer by spin coating, using the γAF 1600 solution, and a doublefaced tape-pasted metallic support frame was bonded to the organic thinfilm formed on the treated silicon wafer and peeled from the siliconwafer at 23° C. and a relative humidity of 50%, whereby the organic thinfilm could be easily peeled from the silicon wafer.

[0108] The resulting organic thin film was free from any wrinkles, colorunevenness, traces of peeling and transferred matters from the substrateand was thus found satisfactory. The light transmittance at thewavelength of 248 nm was as high as 99.6% and the film thickness wasuniform and satisfactory.

[0109] The silicon wafer surface that was peeled off the organic thinfilm had no traces of peeling and had a contact angle of the surface towater of 108°, and the silicon wafer was repeatedly used as a recyclesilicon wafer.

[0110] Further organic thin films were repeatedly on the same recyclesilicon wafer that was peeled off the organic thin film just before inthe same manner as above, followed by peeling the just formed organicthin film, and it was found that 10 recyclic uses of the same recyclesilicon wafer could be made.

[0111] The resulting organic thin films were all free from any wrinkles,color unevenness, traces of peeling and transferred matters from thesubstrate and were thus found satisfactory. The light transmittance atthe wavelength of 248 nm was as high as or higher than 99.6%, and thefilm thickness was uniform and satisfactory.

[0112] Even after the 10 recyclic uses, the silicon wafer surface had notraces of peeling and had the same contact angle of the substrate towater of 108° as before the formation of the organic thin films.

COMPARATIVE EXAMPLE 1

[0113] An organic thin film was formed on a polished silicon waferhaving a contact angle of the surface to water of 51° by spin coating,using the CYTOP solution in the same manner as in Example 1. Then, adouble faced tape-pasted metallic support frame was bonded to theorganic thin film formed on the silicon wafer, followed by peeling fromthe silicon wafer at 23° C. and a relative humidity of 50%, but it wasfound that the peeling was so hard that the organic thin film was brokenduring the peeling and failed to peel.

COMPARATIVE EXAMPLE 2

[0114] An organic thin film was formed on a polished silicon waferhaving a contact angle of the surface to water of 51° by spin coating,using the γAF 1600 solution as in Example 2. Then, a double facedtape-pasted metallic support frame was bonded to the organic thin filmformed on the silicon wafer, followed by peeling from the silicon waferat 23° C. and a relative humidity of 50%, it was found that the peelingwas so hard that the organic thin film was broken during the peeling.There were many remains of the organic thin film layer on the siliconwafer surface. Partially obtained organic thin film had many clouds andmuch color unevenness and the light transmittance at the wavelength of248 nm was as low as 50 to 80%.

COMPARATIVE EXAMPLE 3

[0115] As in Example 1,10,10,10,9,9,8,8,7,7,6,6,5,5,4,4,3,3-heptadecafluoro-decyltrimethoxysilaneand a polished silicon wafer were placed into a metallic vessel,followed by tight sealing. Then, the metallic vessel and its inside wereheated to 105° C., left for standing in that state for 36 hours, andcooled to room temperature. The treated silicon wafer was taken out ofthe metallic vessel. It had a contact angle of the surface to water of103°, whereas the untreated polished silicon wafer had a contact angleof 51°.

[0116] Then, nitrocellulose was dissolved into propyleneglycolmonomethyl ether to make a 6.0 wt. % nitrocellulose solution.

[0117] The treated silicon wafer was set to a spin coater, and thenitrocellulose solution was filtered through a membrane filter having apore size of 0.2 μm. The filtrate was subjected to spin coating,followed by drying on a hot plate, whereby an organic thin film having athickness of 0.84 μm was formed. A double faced tape-pasted metallicsupport frame was bonded to the organic thin film formed on the siliconwafer, followed by peeling from the silicon wafer at 23° C. and arelative humidity of 50%, but it was found that the peeling was so hardthat the organic thin film was broken during the peeling.

EXAMPLE 6

[0118] An open top polyethylene container, 5 cm in diameter, containing20 ml of10,10,10,9,9,8,8,7,7,6,6,5,5,4,4,3,3-heptadecafluoro-decyltrimethoxysilaneand a polished wafer were placed into a 30 cm-square metallic vessel,followed by tight sealing. The metallic vessel and its inside wereheated to 105° C., left for standing for 36 hours, and cooled to roomtemperature. The treated silicon wafer was taken out of the metallicvessel. It had a contact angle of the surface to water of 110°, whereasthe untreated polished silicon wafer had a contact angle of 51°.

[0119] Then, Teflon AF 2400 (trademark of a product commerciallyavailable from E.I. du Pont de Nemour & Co., Inc., USA) was irradiatedwith γ-rays in air at an irradiation dose of 300 kGy (Gy: dose unit),which will be hereinafter referred to as “γAF 2400”. The γAF 2400 wasdissolved into perfluorotributylamine to make a 1 wt. % solution.Cellulose acetate propionate CAP 482-20 (trademark of a productcommercially available from Eastman-Kodak Co., USA), which will behereinafter referred to as “CAP”, was dissolved into propyleneglycolmonomethyl ether. The resulting solution had a viscosity of 400 c poise(25° C.).

[0120] At first, the treated silicon wafer was set to a spin coater, andthe γAF 2400 solution was filtered through a membrane filter having apore size of 0.2 μm. 5 cc of the filtrate was dropwise added to thesilicon wafer, followed by revolution of the silicon wafer at 600 rpmfor 30 seconds, air drying and further drying on a hot plate, whereby areflection-preventing layer was formed on the silicon wafer. Then, theCAP solution was filtered through a membrane filter having a pore sizeof 0.2 μm, and 20 ml of the filtrate was dropwise added to thereflection-preventing layer, followed by revolution of the silicon waferat 1,000 rpm for 45 seconds and evaporation of the solvent on a hotplate, whereby a 1.2 μm-thick thin film (central layer) composed of CAPwas formed on the reflection-preventing layer on the silicon wafer.

[0121] Furthermore, 5 ml of the filtrate of the γAF 2400 solution wasdropwise added to the central layer, followed by revolution of thesilicon wafer at 600 rpm for 30 seconds, air drying and further dryingon a hot plate, whereby a further reflection-preventing layer wasformed. That is, a triple layer film was obtained. Thereflection-preventing layers formed on both sides of the central layereach had a thickness of 73 nm.

[0122] Then, a double faced tape-pasted metallic support frame wasbonded to the triple layer film formed on the silicon wafer. The triplelayer film could be easily peeled from the silicon wafer at 23° C. and arelative humidity of 50%.

[0123] The resulting triple layer pellicle film was free from colorunevenness, traces of peeling and transferred matters from the substrateand was thus found satisfactory. The silicon wafer surface that waspeeled off the pellicle film had no traces of peeling and had the samecontact angle of the surface to water of 110° as before the formation ofthe pellicle film.

[0124] Then, a further triple layer pellicle film was formed again onthe silicon wafer that was peeled off the pellicle film by spin coatingin the same manner as above. A double faced tape-bonded metallic supportframe was likewise bonded to the triple layer film formed on the siliconwafer. The triple layer film could be easily peeled from the siliconwafer at 23° C. and a relative humidity of 50%.

[0125] The resulting triple layer pellicle film was free from colorunevenness, traces of peeling and transferred matters from the substrateand was thus found satisfactory. The silicon wafer surface had no tracesof peeling and had a contact angle of the surface to water of 110°, andthe silicon wafer was repeatedly used as a recycle silicon wafer.

[0126] Further triple layer pellicle films were repeatedly formed on thesame recycle silicon wafer, followed by peeling from the silicon wafer.30 cyclic uses of the same recycle silicon wafer could be made. Theresulting triple layer pellicle films were all free from colorunevenness, traces of peeling and transferred matters from the substrateand were thus found satisfactory. Even after the 30 cyclic uses, therecycle silicon wafer surface had no traces of peeling and had the samecontact angle of the surface to water of 110° as before the formation ofthe pellicle films.

EXAMPLE 7

[0127] As in Example 6,10,10,10,9,9,8,8,7,7,6,6,5,5,4,4,3,3-heptadecafluorodecyltrimethoxysilaneand a polished silicon wafer were placed into a metallic vessel,followed by tight sealing. The metallic vessel and its inside wereheated to 30° C., left for standing in that state for 24 hours, andcooled to room temperature. The treated silicon wafer was taken out ofthe metallic vessel. It had a contact angle of the surface to water of103°, whereas the untreated polished silicon wafer had a contact angleof 51°.

[0128] As in Example 6, a reflection-preventing layer, a central layerand another reflection-preventing layer were successively formed in thisorder on the treated silicon wafer by spin coating to form a triplelayer pellicle film. A double faced tape-pasted metallic support framewas bonded to the triple layer film formed on the silicon wafer, and thethus formed triple layer film could be easily peeled from the siliconwafer at 23° C. and a relative humidity of 50%. The resulting triplelayer pellicle film was free from color unevenness, traces of peelingand transferred matters from the substrate and was thus foundsatisfactory. The silicon wafer surface that was peeled off the triplelayer film had no traces of peeling and had a contact angle of thesurface to water of 103°, and the silicon wafer was repeatedly used as arecycle silicon wafer.

[0129] Further triple layer pellicle films were repeatedly formed on therecycle silicon wafer, followed by peeling. Ten recyclic uses could bemade. The resulting triple layer pellicle films were all free from colorunevenness, traces of peeling and transferred matters from the substrateand were thus found satisfactory. Even after the 10 recyclic uses, therecycle silicon wafer surface had no traces of peeling and had the samecontact angle of the surface to water of 103° as before the formation ofthe pellicle films.

EXAMPLE 8

[0130] As in Example 7,10,10,10,9,9,8,8,7,7,6,6,5,5,4,4,3,3-heptadecafluoro-decyltrimethoxysilaneand a polished silicon wafer were placed into a metallic vessel,followed by tight sealing under vessel pressure of 660 mm Hg (−100 mmHg). The metallic vessel and its inside were heated to 30° C., left forstanding in that state for 24 hours, and cooled to room temperature. Thetreated silicon wafer was taken out of the metallic vessel. It had acontact angle of the surface to water of 104°, whereas the untreatedpolished silicon wafer had a contact angle of 51°.

[0131] As in Example 6, a reflection-preventing layer, a central layerand another reflection-preventing layer were successively formed in thisorder on the treated silicon wafer by spin coating to form a triplelayer pellicle film. A double faced tape-pasted metallic support framewas bonded to the triple layer film formed on the silicon wafer, and thethus formed triple layer film could be easily peeled from the siliconwafer at 23° C. and a relative humidity of 50%. The resulting triplelayer pellicle film was free from color unevenness, traces of peelingand transferred matters from the substrate and was thus foundsatisfactory. The silicon wafer surface that was peeled off the triplelayer film had no traces of peeling and had a contact angle of thesurface to water of 104°, and the silicon wafer was repeatedly used as arecycle silicon wafer.

[0132] Further triple layer pellicle films were repeatedly formed on therecycle silicon wafer, followed by peeling. Ten recyclic uses could bemade. The resulting triple layer pellicle films were all free from colorunevenness, traces of peeling and transferred matters from the substrateand were thus found satisfactory. Even after the 10 recyclic uses, therecycle silicon wafer had no traces of peeling and had the same contactangle of the surface to water of 104° as before the formation of thepellicle films.

EXAMPLE 9

[0133] A compound represented by the following general formula (3):

CF₃(CF₂)₅CH₂CH₂Si(OMe)₃  (3)

[0134] where Me is a methyl group, and a polished silicon wafer wereplaced into a metallic vessel, followed by tight sealing. The metallicvessel and its inside were heated to 105° C., left for standing in thatstate for 36 hours, and cooled to room temperature. The treated siliconwafer was taken out of the metallic vessel. It had an contact angle ofthe surface to water of 108°, whereas the untreated polished siliconwafer had a contact angle of 51°.

[0135] As in Example 6, a reflection-preventing layer, a central layerand another reflection-preventing layer were successively formed in thisorder on the treated silicon wafer by spin coating to form a triplelayer pellicle film, and a double faced tape-pasted metallic supportframe was bonded to the triple layer film formed on the silicon wafer.The triple layer film could be easily peeled from the silicon wafer at23° C. and a relative humidity of 50%. The resulting triple layerpellicle film was free from color unevenness, traces of peeling andtransferred matters from the substrate and was thus found satisfactory.The silicon wafer surface that was peeled off the triple layer film hadno traces of peeling and had an angle of the surface to water of 108°and the silicon wafer was repeatedly used as a recycle silicon wafer.

[0136] Further triple layer pellicle films were repeatedly formed on thesame recycle silicon wafer, followed by peeling from the recycle siliconwafer. Ten recyclic uses could be made. The resulting triple layerpellicle films were all free from color unevenness, traces of peelingand transferred matters from the substrate and were thus foundsatisfactory. Even after the 10 recyclic uses, the silicon wafer surfacehad no traces of peeling and had the same contact angle of the surfaceto water of 108° as before the formation of the pellicle films.

COMPARATIVE EXAMPLE 4

[0137] As in Example 6, a reflection-preventing layer, a central layerand another reflection-preventing layer were successively formed in thisorder on a polished silicon wafer by spin coating to form a triple layerpellicle film, and a double faced tape-pasted metallic support frame wasbonded to the triple layer film formed on the silicon wafer, followed bypeeling from the silicon wafer at 23° C. and a relative humidity of 50%.Peeling took place at the boundary between the reflection-preventinglayer in contact with the silicon wafer and the central layer, and thepellicle film attached to the support film was in a double layer, whilethe reflection-preventing layer in contact with the silicon waferremained on the silicon wafer.

What is claimed is:
 1. An organic thin film obtained by forming an organic thin film on the surface of a substrate having a contact angle of the surface to water of 90° or higher, followed by peeling the film therefrom.
 2. An organic thin film obtained by forming an organic thin film comprising a fluorine-based material or a silicon-based material on the surface of a substrate having a layer comprising a silicon compound having a perfluoroalkyl group formed on the surface, followed by peeling the film therefrom.
 3. An organic thin film according to claim 1 or 2, wherein the organic thin film is in a single layer.
 4. An organic thin film according to any one of claims 1 to 3, wherein the organic thin film is a pellicle.
 5. An organic thin film according to claim 1, 2 or 4, wherein the organic thin film is a pellicle comprising a reflection-preventing layer composed of a fluorine-based material and a transparent thin film layer.
 6. An organic thin film according to any one of claims 2 to 4, wherein the layer comprising a silicon compound having a perfluoroalkyl group is formed by vapor deposition.
 7. An organic thin film according to any one of claims 2 to 4, wherein the silicon compound having a perfluoroalkyl group is a compound represented by the following formula (1): CF₃(CF₂)_(n)CH₂CH₂Si(OMe)₃  (1) where n is an integer of 5 to 7 and Me is a methyl group.
 8. A process for producing an organic thin film, which comprises forming an organic thin film on the surface of a substrate having a contact angle of the surface to water of 90° or higher, followed by peeling the film therefrom.
 9. A process for producing an organic thin film, which comprises forming an organic thin film comprising a fluorine-based material or a silicon-based material on the surface of a substrate having a layer comprising a silicon compound having a perfluoroalkyl group formed on the surface, followed by peeling the film therefrom.
 10. A process according to claim 8 or 9, wherein the organic thin film is in a single layer.
 11. A process according to any one of claims 8 to 10, wherein the organic thin film is a pellicle.
 12. A process according to claims 8, 9 or 11, wherein the organic thin film is a pellicle comprising a reflection-preventing layer composed of a fluorine-based material and a transparent thin film layer.
 13. A process according to any one of claims 9 to 11, wherein the layer comprising a silicon compound having a perfluoroalkyl group is formed by vapor deposition.
 14. A process according to any one of claims 9 to 11, wherein the silicon compound having a perfluoroalkyl group is a compound represented by the following formula (1): CF₃(CF₂)_(n)CH₂CH₂Si(OMe)₃  (1) where n is an integer of 5 to 7 and Me is a methyl group. 